The invention is in the field of adjustable wrenches, which includes crescent wrenches, pipe wrenches, and monkey wrenches. These wrenches have in common the fact that they are all adjustable. The jaws of the respective wrench must be capable of expanding or contracting to accommodate a variety of sizes of bolts or pipes, and the wrench must be capable of locking in the engaged mode, and relatively easily disengagable.
Over the years, there have been dozens if not hundreds of adjustable wrench designs, with probably the most popular being the simple, rotary-nut wrench in which one rotates the adjustment nut laterally of the handle or shank of the wrench to open or close the jaws, to achieve the appropriate jaw spacing.
That embodiment of the adjustable wrench has several advantages. First, it is very basic and simple. The loosely threaded, transversely rotating knurled nut used to adjust the wrench is virtually foolproof. It is also fairly easy to make the adjustment mechanism quite strong. And, once adjusted, the sliding jaw will not slip under pressure, although sometimes there may be an undesirable slack in the jaw spacing that must be used up before the sliding jaw become fixed.
With all these advantages, there is still a principle disadvantage in the classic adjustable wrench that has been behind the majority of sliding jaw adjustable wrench innovations. That drawback lies in the fact that adjusting the jaw spacing over a large distance is somewhat tedious and time consuming, requiring repeated rotation of the adjusting nut until the jaws open or close.
The ideal adjustable wrench would have a sliding jaw that is both quite freely slidable when it is not under tension, but becomes instantly immobile when expansive force is applied to the jaws with as little play as possible. The wrench must then have an easily usable sliding jaw release which does not require inordinate force.
The following devices have appeared in U.S. patents over the years in an attempt to provide such a wrench:
______________________________________ PAT. No. ISSUE DATE TITLE INVENTOR ______________________________________ 1. 12,510 March 13, 1855 Pipe J. Hyde Wrench 2. 16,158 December 2, 1986 Wrench O. O. Witherell 3. 26,468 December 20, 1859 Wrench A. J. Bell 4. 61,097 January 8, 1867 Wrench T. Pratt 5. 254,507 March 7, 1882 Wrench Schneider 6. 686,437 November 12, 1901 Wrench G. W. Boozer 7. 705,860 July 29, 1902 Wrench J. O'Brien 8. 753,837 March 8, 1904 Monkey L. C. Barcus Wrench 9. 1,886,146 October 14, 1932 Adj. F. H. Andrews Wrench 10. 1,903,052 March 28, 1933 Wrench J. R. Kerlin 11. 3,563,118 February 16, 1971 A.S.L. E. Rydell Wrench ______________________________________
Quick-adjusting wrenches thus date back to well before the civil war. Typically, they work on either a cam mechanism or a ramp mechanism whereby expansion of the jaws causes a wedge, ramp, or cam to move, creating a resistive expansive force on another member which stops expansion of the jaws. There is generally some type of lever mechanism which pops the ramp or cam free, or at least reduces the pressure on the element substantially, so that the moveable jaw can be easily moved to open the jaws.
The mechanism most closely resembling applicant's device is illustrated in the Boozer patent, U.S. Pat. No. 686,437. In that device, a movable "pressure plate" translates longitudinal jaw motion into transverse pressure against the wrench shank when the sliding jaw expands. Whereas the Boozer wrench might have been viable in its time, it does not optimize stress distribution as it should in order to maximize wrench life, and its mechanism, although advantageous in that it is simple, is somewhat primitive in that it is doubtful whether it would have a smooth sliding action, and its repeated use would seem to scar the inner face of the wrench shank considerably.
There is a need for a simple, quickly adjustable wrench which achieves the above-stated objectives of an optimal quickly adjustable wrench while avoiding the pitfalls of the wrenches disclosed in the above-enumerated patents.